page_title: Inductor
section_title: Choke
hierarchical_section_title: Inductor / Types / Choke
caption_attribution_description: English: en:Ferrite bead
context_page_description: An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a coil around a core.
  When the current flowing through an inductor changes, the time-varying magnetic field induces an electromotive force in the conductor, described by Faraday's law of induction. According to Lenz's law, the induced voltage has a polarity which opposes the change in current that created it. As a result, inductors oppose any changes in current through them.
  An inductor is characterized by its inductance, which is the ratio of the voltage to the rate of change of current. In the International System of Units, the unit of inductance is the henry named for 19th century American scientist Joseph Henry. In the measurement of magnetic circuits, it is equivalent to weber/ampere. Inductors have values that typically range from 1 µH to 20 H. Many inductors have a magnetic core made of iron or ferrite inside the coil, which serves to increase the magnetic field and thus the inductance.
context_section_description: A choke is an inductor designed specifically for blocking high-frequency alternating current (AC) in an electrical circuit, while allowing DC or low-frequency signals to pass. Because the inductor resistricts or "chokes" the changes in current, this type of inductor is called a choke. It usually consists of a coil of insulated wire wound on a magnetic core, although some consist of a donut-shaped "bead" of ferrite material strung on a wire. Like other inductors, chokes resist changes in current passing through them increasingly with frequency. The difference between chokes and other inductors is that chokes do not require the high Q factor construction techniques that are used to reduce the resistance in inductors used in tuned circuits.
caption: An MF or HF radio choke for tenths of an ampere, and a ferrite bead VHF choke for several amperes.
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